To control the actuation speed of a device corresponding to the load applied to the device irrespective of the actuation position by controlling the actuation speed of a movable body arranged in a casing to be approximately constant.

When a force to press a shaft body of a connection member 2 into a casing 1, the load is applied to a movable body 2, and the movable body 2, an elastic member 4, and a rigid body 5 are started to move to the left direction. The compressive force works on the viscous fluid 15 on the left side of the elastic member 4, the fluid pressure presses the rigid body 5 against the elastic member 4, while a part of the viscous fluid 15 flows to the right side of the movable body 2 through a passage 7 whose area is changed by the fluid pressure, a through hole 11, an annular groove 12, and through holes 13, 14. If the load on the movable body 2 is small, the area of the passage becomes large, and if the load is large, the area of the passage becomes small. Even when the load applied to the movable body 2 is fluctuated, the movable body 2 is actuated in the prescribed speed range, and the connection means 3 is moved by the movement of the movable body 2. The actuation speed of the movable body 2 can be controlled to be approximately constant irrespective of the actuation position of the movable body.